Type Inference

👨‍💼 Great detective work! You found and fixed the bug.

When you added : number as the return type, TypeScript immediately flagged the string return as an error. This is why explicit return types can be valuable:

// Without explicit return type - no error, bug ships to production
function divide(a: number, b: number) {
	if (b === 0) return 'error' // 😱
	return a / b
}

// With explicit return type - caught at compile time!
function divide(a: number, b: number): number {
	if (b === 0) return 'error' // ❌ Type 'string' is not assignable to 'number'
	return a / b
}

🦉 The rule of thumb:

Let inference work for simple, obvious functions
Add explicit types for public APIs and when you want to catch this class of bugs early

05. Functions/03. Type Inference (🏁 solution)

Type Inference